Interpretation

Positive:

       Interferon-gamma (IFN-gamma) response to Mycobacterium tuberculosis antigens detected, suggesting infection with M tuberculosis. Positive results in patients at low-risk for TB should be interpreted with caution and repeat testing on a new sample should be considered recommended by the 2017 American Thoracic Society, the Infectious Diseases Society of America, the Centers for Disease Control and Prevention (ATS/IDSA/CDC) Clinical Practice Guidelines for Diagnosis of Tuberculosis in Adults and Children.(1) False-positive results may occur in patients with prior infection with Mycobacterium marinum, Mycobacterium szulgai, or Mycobacterium kansasii.

Negative:

       No IFN-gamma response to M tuberculosis antigens was detected. Latent infection with M tuberculosis is unlikely. A single negative result does not exclude infection with M tuberculosis. In patients at high risk for M tuberculosis infection, a second test should be considered in accordance with the 2017 ATS/IDSA/CDC Clinical Practice Guidelines for Diagnosis of Tuberculosis in Adults and Children.(1)

 Indeterminate due to Low Mitogen Value:

        Indeterminate results due to a low IFN-gamma level in the mitogen (positive control) tube. This may occur due to a low lymphocyte count, reduced lymphocyte activity, or inability of the patient's lymphocytes to generate IFN-gamma.

Indeterminate due to High Nil value:

        Indeterminate results due to a high level of IFN-gamma in the Nil (negative control) tube. This may occur due to heterophile antibody effects or nonspecific, circulating IFN-gamma in the patient's blood sample. Repeat testing on a new specimen is suggested.